I want to upgrade my Rear rotors to cross drilled.

I now have 5lug rears.


Do you know where is the best place to get 5lug,
cross drilled Rear rotors for the 1970 914?


thanks,
Bno

buy the genuine 914-6 rear rotors and have them cross drilled.
Our guy charges us 30 per rotor to do it. The rotors are 95 each.

I recently researched this. George at AA is the only source I found.

Is it safe to cross drill rotors?
Does it create stress risers and potential cracks?

Rich

Debatible.
Yes and yes. You make your mods, you take your risks...

Depends on how hot you plan on getting them, and how often. I would inspect them for cracks every once in a while and replace them if you see any kind of connect-the-dots action going on.

Properly drilled they won't just suddenly fail on you though, and the additional bite they give you might just save your bacon some time in a street car.

Precisely. The key is in the watchful caution.

Why drill them?
I am being somewhat rhetorical...
At what point in your HP upgrade do you feel the need to cross drill the rear rotors on a 914 brake system?

Rich

Rich,
To answer your rhetorical, I think you understand why I didn't. The rear brakes are really only there to make sure the car stops straight in our cars. The market for these is really only in the guys who have to have that bling thing. I only considered it for the view through the Fuchs... The solid 914-6 rotors were available right now, the others were a bit of a wait. I seldom wait patiently.

Rotating unsprung mass in the rear of a car that already has a rear weight bias

Exactly, rotating unsprung mass is the devil.

Do the math on that one...
Its so small you would never feel it.

Rich

Thanks all for the info and input.

I was planning on going to drilled rotors all around,
sourcing the front ones seems quite ez, but
the rear ones are not so easy to find.
Perhaps this reflects a lack of demand.

I will put on some new pads and drive the car
some more before I go ahead with this rotor upgrade.

thanks,
Bno

Your rear brakes do on average, 20% of your braking. Is it a race car?

If I'm doing 150mph to 30 mph many times in a short period of time, I suspect it makes a difference. On the street, not so much.

I would definately NOT have someone cross-drill rotors. Too many potential problems for very, very little gain.

T.C.